


Mammon Takes On Diavolo's Huge Horse Cock

by PrivacyJack



Category: Shall We Date?: Obey Me!
Genre: Bedroom Sex, Breeding, Centaurs, Come Inflation, Fainting, Fingerfucking, I'm Bad At Titles, I'm Sorry, Implied Mpreg, Impregnation, Large Cock, Love Bites, M/M, Marking, Mating Bites, Monsters, Overstimulation, Plot What Plot/Porn Without Plot, Porn, Porn with Feelings, Size Difference, Trans Male Character, Vaginal, Vaginal Fingering, Vaginal Sex
Language: English
Status: Completed
Published: 2021-02-01
Updated: 2021-02-01
Packaged: 2021-03-12 12:26:52
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,972
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29135508
Author URL: https://archiveofourown.org/users/PrivacyJack/pseuds/PrivacyJack
Summary: (READ THE FUCKING WARNINGS IN NOTES)Mammon is tasked with bringing Lucifer's papers to Diavolo just as a storm breaks out and he is forced to stay the night at the castle where he discovers Diavolo's third form which is a centaur. Later he also finds out the form is for breeding and he might just become the next queen. MamDia Supremacy, bitches.-×-×-×-×-×-×-×-×-×-×-Yeah blame another centaur fucking story for this. Lucifer is a fucking whore and does not fucking deserve Diavolo's romantic affection so the next best thing is Mammon. Once again MamDia Supremacy and also trans Mammon rights, fuckers. Also this is the first time I have written actual smut in a very long time so shut it please.-Writer J
Relationships: Diavolo/Mammon (Shall We Date?: Obey Me!)
Comments: 22
Kudos: 101





	Mammon Takes On Diavolo's Huge Horse Cock

**Author's Note:**

> WARNING! THIS STORY CONTAINS VAGINAL SEX, COME INFLATION, BREEDING, HORSE COCKS, AND OTHER SEXUAL CONTENT OF THE CHARACTERS MAMMON AND DIAVOLO FROM THE GAME SHALL WE DATE: OBEY ME! IF THAT ISN'T YOUR THING THEN SHUT THE FUCK UP AND LEAVE!
> 
> However if you like the story you read then don't be afraid to leave a kudos or comment!

Mammon walked down the castle hallway groaning about his current task. Lucifer just had to ask him out of all his brothers to deliver some important papers to Diavolo. It had always been Lucifer's job to do that, but Lucifer still had a lot of paperwork left to do. It wasn't just the fact he had to take the long walk to the castle and walk through what felt like a labyrinth of rooms and halls, it was also the fact it had began to rain on his way there quickly making his hair and clothes drenched in rainwater. So now he was soaking wet with the damn papers.

Mammon grumbled to himself before walking to one of the doors at the end of the hall where Barbatos said Diavolo would be. It was Diavolo's office where the prince did his own share of paperwork and such. Mammon just hoped he could just walk in and get out for he wanted to go home already and get dry. The floor behind him was already soaking wet with the water he brought in. He looked back at the large red door in front of him and sighed before giving a hesitant knock.

"Come in!" He heard the prince's voice from the inside of the room.

Mammon opened the door ready to just drop the now slightly wet papers in Diavolo's possession and leave. He looks up from the papers seeing an unexpected view. Prince Diavolo in what looked like his second form, but much much taller and his legs weren't anywhere to be seen. The lower half of his body was replaced with the body of a horse. Fur as black as the night sky covering a thick body with light grey feathering on his brightly colored hooves.

At the end of his rear was long black hair for a tail which had all kinds of gold accessories covering it and even more gold on the bottom of the hooves for what Mammon supposed were horseshoes. Mammon had not realized how long he was staring until he heard the prince's voice saying his name. The second borne shook his head breaking out of his trance and looked up at Diavolo who looked as surprised as Mammon.

"Mammon? Now, what are you doing here?" Diavolo placed his hands on his hips slowly trotting his way towards the much smaller demon. "I thought it was Lucifer who was supposed to be here at this time."

"I-I uh... Lucifer told me to bring these to you," Mammon held up the papers looking down again. "H-he said he had to get other paperwork done."

"Thank you, Mammon... although I did want Lucifer to come by..." Diavolo mumbled the second part of his sentence before continuing, "oh well, I suppose you'll just have to do then!"

"Wait what does that mean-" Mammon yelped when Diavolo suddenly put his arm around the small male and began leading him out the door. "W-wait I should be gettin' back home now."

"Getting home while it's storming? Nonsense! I wouldn't want Lucifer's little brother coming home sick," Diavolo lead Mammon out back the hallway and down another. "Besides I don't think we have spoken to each other that often and I would like to get closer if that is alright with you."

"I mean... I guess it won't hurt to chat for a bit," a nervous smile appeared on Mammon's face as the two walked down the hall.

Mammon had no clue where Diavolo was taking him, but on their way down another long hallway, they began to talk. One of the first things they spoke of was why Diavolo was suddenly half horse which the prince explained was actually normal for demons of royalty to be. Diavolo continued to explain how the more powerful demons had three forms with the one he was currently in being his strongest and most unseen by the public's eye. A form only some staff and other royals could know about for some odd reason. A reason Mammon didn't try to find out he just wanted to get dry already.

The two demons moved from that topic to another and another and before they knew it both of them were joking and laughing with each other. Mammon never knew how funny the prince was as Lucifer always made it seem like he was some big tough guy when in reality he seemed like a normal demon. He was having such a good time talking with the prince he almost didn't notice how the two walked into a room. Mammon stopped for a moment admiring the well-decorated room. It all looked like it was worth a few Grimm, but his thoughts were interrupted.

"We'll stay in here while we wait for the rain to pass, now get yourself dry," Diavolo smiled at Mammon who was given a fright when a familiar butler appeared from behind him with a couple of fluffy towels and a smile on his face.

Was it just him or did Barbatos look more cheerful than usual? Shoving the thought out of his mind he took a towel and began to dry his hair while Barbatos offered to take his wet coat for him. Even when Mammon told the butler it was alright both Barbatos and Diavolo insisted. Once Mammon was mostly dry the butler came back into the room (surprising the avatar again) to take the now wet towels. Mammon also noticed how Diavolo was still in that third form now sitting in one of the seats of the room.

To Mammon, it looked a tad bit uncomfortable, yet Diavolo appeared to be just comfortable. Once Mammon sat from across the prince, the two continued to talk about different subjects ranging from hobbies to unexpectedly some more personal things. Still, the rain didn't seem to stop, and instead, it turned into a full storm with the occasional thunder scaring the second borne. Diavolo and Mammon were having such fun talking to each other they did not notice how quickly time had passed by until Mammon's phone had vibrated to life.

"Ugh, it's Lucifer," Mammon groaned reading the text from his older brother.

'Mammon, where are you?' He didn't have to hear Lucifer's voice to know when Lucifer was furious. 'You have been gone for almost 2 and a half hours!'

"Oh, shit has it really been hours already?" Mammon checked the time confirming it had been. "Lucifer is really pissed with me." 

"Oh that Lucifer. He's quite stunning, but he never knows when to relax," Diavolo sighed before mumbling. "...or please me..."

"Stunning? He's anything, but stunning if you ask me!" Mammon huffed before thinking of what he should reply to Lucifer's text with. "I think I'll just tell him I'll be back soon I should get going anyways."

"Huh? But it's still storming outside you'd only arrive home with a horrible cold," Diavolo stated before leaning in towards Mammon. "Say, when's the last time you spent some time away from your brothers? I'll tell Lucifer you can stay here for the night and we can continue spending time together!

Diavolo laid his hand on Mammon's knee and leaned in even closer.

"We can even have some fun if you'd like..." Diavolo's yellow eyes became half-lidded with traces of lust in them.

Mammon's face went red in a split second and couldn't control himself from nodding. When did it get so hot in here? Diavolo chuckled at the other demon's reaction before grabbing his phone and typing away. A minute later Diavolo silenced his phone as he put it back down on the glass coffee table.

"Now then where were we?" Diavolo smirked at Mammon who was still blushing.

Mammon could not remember the next part of the night even if he tried to. All he could remember was Diavolo ordering Barbatos to bring them a bottle of wine and some backstabbing sandwiches. One bottle of wine turned into two straight to four with the drunken giggles beginning halfway through the third bottle. Once they were a quarter into the fifth, Mammon suddenly found him laying on Diavolo's bed with the centaur standing in front of him. Already Mammon could feel the fabric covering his crotch become wet.

"At first I wanted Lucifer to be in your current position," Diavolo leaned down enough to whisper to Mammon, "but you will do more than fine."

In an instant, Diavolo tore apart Mammon's pants from the smaller demon's legs and threw them to the side. His shirt and boxers followed the same fate as the pair of jeans leaving Mammon completely naked and exposed including his wet pussy. Diavolo smirked sliding his fingers to the lips and beginning to slither a finger in getting a moan out of the other demon.

"Oh wow I didn't expect you to be so tight," Diavolo slid his finger in deeper causing the demon below him to moan louder. "But that definitely won't be a problem."

Diavolo chuckled adding another finger into Mammon feeling his fingers stretch the tight vaginal walls. Mammon was already tearing up and nearing an orgasm with his moans becoming louder every time Diavolo moved his fingers even slightly. Diavolo's large fingers began thrusting in a scissoring pattern careful not to accidentally hurt Mammon with his claws.

"If you think this is too much then you're surely going to be surprised when I stick my dick in you," Diavolo chuckled at the whimpering demon below him.

Mammon wanted to beg Diavolo to put another finger in, but as if on cue Diavolo added another. A loud yelp erupted from the throat of the greedy demon's throat. This wasn't even the best part and he was already beginning to orgasm coating Diavolo's fingers in his vaginal fluids.

"H-holy fuck you're soaked I can't wait to stick it in you," Diavolo continued to move his in and out of Mammon knowing if he'd add a fourth they'd breeze by another orgasm from Mammon.

Diavolo had not even orgasmed once yet, but his dick was becoming harder as Mammon came closer to his next orgasm. In his normal form, his dick was naturally 7 inches, but in his third, it was no smaller than a full foot and 6 inches wide in the form of a horse cock. He had never had sex in this form as it was usually saved for when royals were breeding their mates to ensure they and their partners have offspring. If Diavolo could not have that experience with Lucifer then he would gladly take the next best option. Although with how amazing this was going Mammon might just be the better option.

Diavolo slid his fingers out of Mammon leaving the now unfilled brother panting and letting out soft delicate moans. Mammon felt sweat drip down his face and the rest of his heated breathing body before looking at the prince who was moving forward. Next thing he knew Diavolo was positioning himself so the tip of his massive dick was just mere inches away from Mammon's still very tight entrance. The tip was almost bigger than Mammon's delicate hole sending a chill up the smaller demon's spine at the sight. Yet surely something this massive would feel amazing inside of him so would it really hurt more than it felt good?

He just had to find out. Diavolo had his front hooves kneeling on the bed pinning Mammon to the bed with Diavolo's tip barely touching Mammon's clit.

"D-Diavolo... fuck me now p-please- AH!" Mammon's face went from half-lidded with lust to shocked at the feeling of Diavolo thrusting his entire tip into Mammon's hole. "O-OH MY FUCKING G-GOD!"

"H-holy shit you're so tight," Diavolo felt like his dick was being squeezed the further he went in. "Y-you're already so much better than Lucifer."

Before Mammon could even process Diavolo's slurred words the prince began moving forward making Mammon scream from all the mixed feeling. He was filled with the feeling of pleasure and pain, but it felt so wonderful he needed more even if it hurt. His next orgasm was already coming close.

"Oh, my f-fuck! P-please m-more give me more!" Mammon yelled gripping the sides of Diavolo's horse body letting his sin consume him with the need for more of Diavolo's dick.

"H-hold on you're so tight I don't think I can fit the rest of it in you," Diavolo muttered before feeling Mammon release another orgasm that coated his dick.

The greedy demon began thrusting his hips against Diavolo's cock still wanting more while releasing much more screams of pleasure. An unsuspecting bystander would think someone was being tortured in the other room, but nope just the avatar of greed getting his brains fucked out. Diavolo's dick was barely halfway into Mammon when a huge bulge formed in the second demon's stomach. No matter what they would try that was all that was going to fit in Mammon or else the poor boy would tear. Then they would be no fun.

"O-okay time to get moving," Diavolo grunted using much of his energy to pull back slowly before ramming back into Mammon making both of them moan with Mammon's moan sounding more like a scream. "Fuck you're definitely better than Lucifer! H-how about I come inside you then you'll have something, not even your older brother has!"

Mammon screamed feeling the ginormous log of meat move out and back into him with Diavolo leaning down enough for the tiny demon to hear him.

"My offspring... kings only go into their third forms to breed and I can give you as many as you want..." Diavolo began to huff thrusting into Mammon for a third time now. "W-would you like that? My cum filling you up with my heirs? Want to be my queen, you greedy little whore?"

It took a moment or two for the now ruined demon below Diavolo could respond, but his answer was clear from the very beginning.

"Y-yes! Please make me your q-queen! Come in me p-please! B-breed me until I'm c-completely full!" Mammon practically screamed his answer digging his nails into whatever he grabs onto whether it be a part of Diavolo's body or the bedsheets.

A smirk spread across Diavolo's right as he began to speed up the pace wasting no more time in thrusting his cock in and out of Mammon. A burning sensation formed inside of Mammon that a mixture of extreme pain, but most of it was drowned out with the feeling of pleasure. Another feeling in him was the feeling of being split open by Diavolo's huge cock. It was proving to be too much for Mammon as he felt himself becoming limp and his eyes becoming heavy with tiredness. Diavolo wasn't even that close to being finished and he was already getting overstimulated. 

"S-stay with me, I'll make you feel so good," Diavolo growled and fastened his thrusting pace. "Y-you just keep moaning for me, okay?"

And that was what Mammon did. With every thrust and moment Diavolo went faster, he released screams of his stirring excitement while his prostate was abused to the point he thought he was going to pass out soon, but Diavolo wouldn't let him. This feeling was so amazing and nothing he had ever felt before could compare to it. The feeling of being bred was astonishing he wanted more and more like the greedy slut he was. The hours of this bled into what felt like days and into eternity when Diavolo was coming close to his orgasm.

Mammon had since lost his sense of almost everything including time and probably even his own name. Diavolo began whimpering feeling how close he was and began to wonder if Mammon would be able to take on what he had next for the small demon. They'd just have to find out as Diavolo let out a loud groan and stopped thrusting as he began to come inside of Mammon. If either of them thought the bulge in Mammon's belly was big already they were in for another surprise as the gallons of cum that came from Diavolo's huge cock was filling Mammon like a hose attached to a ballon at full blast. Mammon looked at his stomach which swelled larger filling up with Diavolo's cum.

Expectedly the cum began to drip out of Mammon even with Diavolo still in him. The second Diavolo finished coming inside of Mammon, who had another orgasm of his own, the smaller demon began feeling light-headed and blacked out. Both of theirs bodies were covered in sweat and their juices. The storm had turned into a much calmer rain which helped drown out the sound of one of their phones being spammed with notifications from Lucifer. It did not matter though as Diavolo has found the better option for himself.

The second he pulled out of Mammon his cum came pouring out of the boy's abused hole. Diavolo called Barbatos on to help him with the aftercare, but not before leaning back down to the demon below him and biting down on the side of Mammon's neck leaving behind a large and most likely permanent bite mark. Diavolo had made sure it was in a place that was not too noticeable, but just in the right place so when needed he or Mammon can show any other demon that Mammon was his and only his whether anyone else liked it or not. He had originally been hoping for Lucifer to be in Mammon's place and wondered if Lucifer would have been more enjoyable, but now that it was actually happening and the image of Mammon below him was turning him on more than the thought of Lucifer...

Diavolo knew he made the right choice of breeding Mammon instead.

**Author's Note:**

> I'm fucking wondering if I should make a second chapter with pregnant Queen Mammon. Maybe I will if you guys give this enough love and attention.
> 
> -Writer J


End file.
